MyFirstProgram Assignment

kavya

Lesson1-IntroToProgrammingWithPython.pdf

Home >Computer Science homework help >MyFirstProgram Assignment

An Introduction to Programming Using Python David I. Schneider

An Introduction to Computing and Problem Solving

Lesson 1

Questions and Answers

• How do we communicate with the computer?

– Programming languages

• How do we get computers to perform complicated tasks?

– Tasks are broken down into a sequence of instructions

• Why Python?

– Powerful, easy to download, write and read

Questions and Answers • How did the language Python get its name?

– Named for the British comedy group Monty Python (really!)

• Book uses the editor IDLE to create programs. How did IDLE get its name?

– Stands for Integrated DeveLopment Environment

• What is an interpreted language?

– Uses an interpreter, translates high-level language one statement at a time into machine language and then runs

Questions and Answers

• What are the meanings of the terms “programmer” and “user”?

– Programmer: a person who solves problems by writing programs on a computer

– User: any person who runs a program

• What is the meaning of the term “code”?

– Python statements that the programmer writes

Questions and Answers

• Are there certain characteristics that all programs have in common?

– Input, processing, output

• What are the meanings of the terms “hardware” and “software”?

– Hardware: physical components of the computer

– Software: the programs

Questions and Answers

• How are problems solved with a program?

– Step-by-step procedure devised to process given data and produce requested output.

• What is a zero-based numbering system?

– Numbering begins with zero instead of one

• Prerequisites to learning Python?

– Be familiar with how folders and files are managed

Questions and Answers

• What is an example of a program developed in this textbook?

FIGURE 1.1 A possible output for a program in Lesson 2.

Questions and Answers

• How does the programmer create such a program?

– About ten lines of code that search a text file named USpres.txt and extract the requested names.

Questions and Answers

• What conventions are used to show keystrokes?

– key1+key2 means “hold down key1 and then press key2”

• Ctrl+C places selected material into the Clipboard

– key1/key2 means “Release key1 and then press key2”

• Alt/F opens the FILE menu on a menu bar.

Questions and Answers

• How can the programs for the examples in this textbook be obtained?

– See the preface for information

• Where will new programs be saved?

– Create a special folder to hold your programs

• Where can I research questions I have about Python?

– Documentation at https://www.python.org/doc/

https://www.python.org/doc/

Program Development Cycle

FIGURE 1.2 The problem solving process.

Program Planning

1. Analyze: Define the problem.

2. Design: Plan the solution to the problem.

3. Code: Translate the algorithm into a programming language.

4. Test and correct: Locate and remove any errors in the program.

5. Complete the documentation: Organize all the material that describes the program.

Programming Tools

• Algorithms

• Flowcharts

• Pseudocode

• Hierarchy charts

Algorithm Development

Algorithm to determine number of stamps for a letter

• Rule of thumb: 1 stamp for every 5 sheets of paper

1. Request sheets of paper

2. Divide by 5

3. Round quotient up to next whole number

4. Reply with number of stamps

Problem Solving for Stamps

FIGURE 1.3 The problem solving process for the stamp problem.

Flowcharts

Example Flowchart

FIGURE 1.4 Flowchart for the postage-stamp

problem.

Pseudocode

• Abbreviated plain English version of actual computer code

• Symbols used in flowcharts replaced by English-like statements

• Allows programmer to focus on steps required to solve problem

Example Pseudocode

FIGURE 1.5 Pseudocode for the postage stamp problem.

Hierarchy Chart

• Shows the overall program structure

• Depict organization of program, omit specific processing logic

• Describe what each part, or module, of the program does

• Each module subdivided into a succession of submodules

Example Hierarchy Chart

FIGURE 1.6 Hierarchy chart for the postage-stamp problem.

Decision Structure

FIGURE 1.7 Pseudocode and flowchart for a decision structure.

Direction of Numbered NYC Streets Algorithm

• Problem: Given street number of one-way street in New York City, decide direction of street, either eastbound or westbound.

• Discussion: There is a simple rule to tell the direction of a one-way street in New York City: Even-numbered streets run eastbound.

Direction of Numbered NYC Streets Algorithm

• Input: Street number.

• Processing: Decide if the street number is divisible by 2.

• Output: “Eastbound” or “Westbound”.

Direction of Streets Algorithm

FIGURE 1.8 Flowchart for the

numbered New York City

streets problem.

Direction of Streets Algorithm

FIGURE 1.9 Pseudocode for the numbered New York City streets problem.

Direction of Streets Algorithm

FIGURE 1.10 Hierarchy chart for the numbered New York City streets problem.

Repetition Structure

• A programming structure that executes instructions many times

– Repetition structure

– Looping structure

• Need a test (or condition) to tell when the loop should end

– Check condition before each pass through loop

Direction of Streets Algorithm

FIGURE 1.11 Pseudocode and flowchart for a loop.

Class Average Algorithm

• Problem: Calculate and report the average grade for a class.

• Discussion: Average grade equals sum of all grades divided by number of students.

– Need loop to read and then add (accumulate) grades for each student in class.

– Inside the loop, we also need to total (count) number of students in class.

Class Average Algorithm

• Input: Student grades.

• Processing: Find the sum of the grades; count the number of students; calculate average grade = sum of grades / number of students.

• Output: Average grade

Class Average Algorithm

FIGURE 1.12 Flowchart for the class average problem.

Class Average Algorithm

FIGURE 1.13 Pseudocode for the class average problem.

Class Average Algorithm

FIGURE 1.14 Hierarchy chart for the class average problem.

How to get Python compiler

• Go to: https://www.python.org/downloads/

• Follow instruction’s on how to install python on your favorite Operating system.

• If this is your first time using a programming compiler you are encourage to do the tutorials.

https://www.python.org/downloads/

Starting IDLE

• Windows: Invoke with double click of

• MAC: Open Finder, select Applications, select the Utilities folder, select Terminal, and then enter IDLE at the prompt

• LINUX and UNIX: usually be found at /usr/bin/idle3

Starting IDLE

FIGURE 1.16 The Python shell.

Starting IDLE

FIGURE 1.17 The Python shell after the expression 2 + 3 has been evaluated.

Starting IDLE

FIGURE 1.18 The Python shell after the statement print(“hello CS625 Class ") has been executed.